I have two TBHs that were started mid-April. They're both getting pretty full at this point (one has 4 bars till full, and the other 7, hives are 4ft long), and so I'm starting to worry about swarming. I had a bad year last year where my one hive (only had one then) swarmed, and the new queen didnt take, so I'm a bit nervous this year.

So far I've been managing them by placing empty bar into the brood nest to give them space to continue to grow. But, now that we're getting to the end of the hive I can't do that anymore. And I don't want to make nucs, cause I don't have the space for another hive. As of today 90% of the comb has brood at some stage, from egg to capped (even saw a few breaking out today). There are a couple with just honey at the front of both, and one or two at the back, and one that is mostly full of pollen in the middle. Here are my questions:

1. You're supposed to keep the brood nest "open", and that's why you're supposed to be adding empty bars to the brood nest. However, the more bars you add to the brood nest, the more it expands, the more bees that are born, and then you have a ton of bees, which I would think would make them feel crowded and then trigger a swarm. So when do you stop adding them to the brood nest? At the stage that I'm at should I stop adding them since the hive is almost full (should I have stopped earlier)? Or do I add them till the hive is full, and then leave the brood nest alone and just start taking honey in order to give them space?

2. When the hive gets full, and the brood nest can't expanding anymore, I'll need to be pulling combs of honey and replacing them with empty bars which will give the workers something to do, which will make them less likely to swarm, correct?

I know there are a lot of factors that determine if a hive will swarm, and often there are no 100% correct answers. Just looking for some guidance based on past experience.

Some colonies will swarm every year unless you do a split or something to make them think they have swarmed. (I don't do any swarm control these days)

I would be tempted to just give them space outside the brood nest now. and let them have the full space. If they really want more space for brood, they will move the honey to the outside. (In a vertical hive they will move honey upwards assuming there is space to do so.)

It is getting a little late here for swarms - most years, the last one I pick up is about the end of May but as you say there are so many variables.........

As catchercradle says, it depends on the bees. Usually once you get past the summer solstice the urge to swarm decreases. I'm a bit further North than him and June is usually my swarming month for standard size colonies although I have small volume hives that I use to produce early swarms.

I think that if you hope to prevent swarming purely by adding bars into the brood nest, or even just giving them more space, you are likely to be disappointed .... if not this year, then definitely next year. Making a split, even just a small split, would be an insurance policy in case of another queen failure and perhaps buy you time to get past the peak swarming period. If the split survives, you have the chance to reunite later in the year when the colony is shrinking back or maintain it over winter and sell it as a nuc next spring or utilise if you suffer a main colony winter loss.

I'm curious to know if you started these colonies with a package or a nuc and if so, how much you fed them? From what I have read, people are recommended to feed packages several gallons of syrup over a 6-8 week period to build up fast, when in my opinion a slow steady build up with just a pint or two of syrup to help them, would be preferable in this situation. Of course you may just live in an area with an abundance of nectar rich plants that the bees have benefitted from and you haven't fed them huge quantities of syrup.

There are benefits to swarming or having a broodless period caused by a split, so if you are able to make a split and remove the queen into the new colony, it will knock the varroa mite population and make them better able to survive without treatment.

Unfortunately the urge to reproduce is a primal one and therefore trying to prevent swarming can be a frustrating task.... like Dave, I gave up a few years ago and enjoy my beekeeping so much more since then. I appreciate that those living in more residential areas cannot always afford that luxury and may need to take preventative measures and doing a split is standard method. Your other option would be to find the queen and clip her wings..... something that I don't personally like..... but everyone has to make their own decisions based on their own circumstances. Then if they do swarm, you at least aren't going to lose them or cause a nuisance to others..... of course you may still get cast swarms unless you do some further intervention.

I'm sorry there are no easy answers. Beekeeping is a craft learned by experience over many seasons. Local forage conditions, climate and bee genetics all play a big part in the decisions you make. In your situation I would probably split the one with less room into a nuc and leave the other one with as much space as you can but still allowing inspection room and perhaps harvesting a bar of honey if they have one capped.

Catchercradle, you said they'll likely swarm unless I split them or do something else to think they have already swarmed. Do you know of other things I can try?

Barbara, I started both hives as packages. I fed them for the first 3 weeks, and probably only a gallon total between both hives. We had a wet winter, and so there was a lot of growth in early spring and they were able to quickly stock the hive and provide for themselves.

I would love to just let nature take its course and have them do what they want, but I am worried about my neighbors. I worry about them swarming and then finding a spot in someone's roof or wall and become a nuisance. But I also don't really want to clip the queen's wings. Maybe I'll have to look into splitting the more populated hive.

When you say you would "leave the other one with as much space as you can" do you mean I should remove the follower board now and let them have access to the entire hive? Would you continue to place bars into the brood nest? Should I stop adding bars to the brood nest in the more populated hive?

Just check with the demeter organic beekeepers and learn about anticipated swarm, etc. You simply check every week as soon as the y have started to built queen cells. When the first is about to be sealed you make an artificial swarming leafing you with the old queen and part of the told colony plus one or more new swarms with swarm cells. Of course you will need new boxes finally.
How much cells does the queen need for laying 2000 eggs in 21 days? 40000. Now you can calculate how many brood combs you need for that. If you give more in spring it is more difficult to keep the brood nest warm which is essential in spring. Evenmore the bees will fill the extra space with pollen. There the queen cannot lay eggs. To tear apart the brood nest by inserting top bars is counterproductive because again the warmth is critical here. When nectar flow sets in the brood nest is not to be expanded.

Conserving wild bees

Research suggests that bumble bee boxes have a very low success rate in actually attracting bees into them. We find that if you create an environment where first of all you can attract mice inside, such as a pile of stones, a drystone wall, paving slabs with intentionally made cavities underneath, this will increase the success rate.

Most bumble bee species need a dry space about the size a football, with a narrow entrance tunnel approximately 2cm in diameter and 20 cm long. Most species nest underground along the base of a linear feature such as a hedge or wall. Sites need to be sheltered and out of direct sunlight.